It's worth noting that for some reason there's a deadline for flashing the generic Bluetooth firmware onto a Stadia controller though, you have to get it done before the end of this year if you have one gathering dust.
Well, a community effort to reverse engineer the process and deobfuscate the javascript is keeping the tool alive. If they didn't step in to archive it, seemingly the cutoff would have been real.
It would have been a better testament to their commitment to prevent these controllers from becoming e-waste if Google just hosted an open source version of the flashing tool on their github from the start.
As far as I know, the reverse engineering/deobfuscation is only for the purpose of allowing third-party firmware to be flashed instead of the Google firmware for Bluetooth. If all you want to do is archive the tool for the latter, you merely have to copy the files from Google's site.
To be fair, they've extended that deadline a few times already (and it's mirrored elsewhere, as another pointed out).
I know Google graveyards a lot of things, but in the Stadia case, they truly went above and beyond to make customers whole again. They refunded every software & hardware purchase automatically, in full, no matter when you bought it, and also provided save game exports. That means people got to play those games on Stadia for those few years, then got all their money back AND some free hardware (Bluetooth controllers). It was a failed Google experiment, but all us guinea pigs got some free entertainment and swag out of it. Kudos.
https://stadia.google.com/controller/index_en_GB.html